Protective helmet



FIG. 1 is front elevational view of a protective helmet;

FIG. 2 is a left side elevational view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a bottom, right perspective view thereof; and,

FIG. 7 is top, left perspective view thereof. 

The ornamental design for a protective helmet, as shown and described. 